South Africa are going to give World Cup-winning lock Johann Muller and star flanker Heinrich Brussow every chance to prove their fitness ahead of their Tri-Nations opener against Australia in Sydney on Saturday.

The duo, battling hamstring and knee injuries respectively, trained on their own on Monday as the Springboks held their first field session in Australia in preparation for the ANZ Stadium showdown with the Wallabies. All the other 26 squad members took a full part in the session, which Springbok coach Peter de Villiers said was designed to loosen up the players after the delayed flight to Sydney on Saturday night.

"The boys had a good run out to shake the trip out of their systems and we're back in the full swing now," said De Villiers. "Johann and Heinrich are coming along nicely and we'll give them another 24 hours before making a final decision."

The Springboks are set to name a new-look side on Tuesday with 21 players missing the tour through injury including lock Victor Matfield, hooker Bismarck du Plessis and winger Bryan Habana. But squad hopeful Adrian Jacobs has warned Australia not to underestimate their second-string side - a fact increasingly unlikely after their 32-23 humbling at the hands of Samoa on Sunday.

"We've got guys in the squad who have played Test rugby before and all of us are looking forward to playing," Jacobs told AFP. "We want to show the world we didn't come over here to fool around. We're here to play rugby.

"There are a lot of places in the side still open and the guys at home will know that many of this team can go to the World Cup and this is an opportunity for every player to show that they are good enough to wear the jersey."

The 30-year-old expects nothing but a fired-up Wallabies challenge, adding: "It was a bit of a surprise for all of us, but Australia is a proud nation and, like all good teams, they will bounce back, hopefully not this week."

The Springboks have also sent messages of congratulations to President Nelson Mandela who celebrates his 93rd birthday today. "On behalf of the entire South African rugby fraternity I want to congratulate Madiba on his 93rd birthday. He is an icon of inspiration not only for South Africans, but for everyone who cherish the idea of a free, democratic and peaceful world," said SARU President, Oregan Hoskins.

"I cannot express in words what Madiba has done for this country and its people and we are indeed privileged to celebrate this special day with him. It is our sincere wish that the Almighty bless him with good health and much strength. Thank you Mr Mandela for what you have done for our country and we want to wish you a very happy and joyous birthday."

De Villiers echoed those sentiments, adding: "He has been very special to our sport - but then he has been very special to our country and the world as well. We have learnt so much from him. He has taught about forgiveness, tolerance, wisdom and humility and they're lessons we should never forget.

"The miracle he produced in this country is something for which we will always be grateful. His example is one that is hard to follow, but one that it is essential we keep copying for decades to come."